I think he's spot on with the overall piece, but I think Twitter is a fine example of the principle too. Twitter was a single-player tool for me at the start. I signed up after hearing about it around SXSW 2006 but there was no-one I knew on there so I just used it as a personal "microjournal" of sorts for several months as it was lighter than the Movable Type setup I was then using (which was amazingly slow at the time). It then became a network for me as people followed me via my email address.
John Gruber's podcast, touches upon this in the recent episode with Ben Thompson as a guest https://daringfireball.net/thetalkshow/2015/01/24/ep-108
